login
A004612
Numbers that are divisible only by primes congruent to 2 mod 3.
10
1, 2, 4, 5, 8, 10, 11, 16, 17, 20, 22, 23, 25, 29, 32, 34, 40, 41, 44, 46, 47, 50, 53, 55, 58, 59, 64, 68, 71, 80, 82, 83, 85, 88, 89, 92, 94, 100, 101, 106, 107, 110, 113, 115, 116, 118, 121, 125, 128, 131, 136, 137
OFFSET
1,2
COMMENTS
Square roots of numbers n such that n-th coefficient of eta(x)^3/eta(x^3)=-1, where eta(x) is given by A010815. - Benoit Cloitre, Oct 06 2005
Apparently the complement to A135412. - R. J. Mathar, Aug 21 2016
EXAMPLE
2=2, 4=2^2, 5=5, 8=2^3, 10=2*5, 11=11, 16=2^4, 17=17, 20=2^2*5, 22 = 2*11, 23=23, 25=5^2, 29=29... (products of powers of elements of A003627). - R. J. Mathar, Jan 22 2021
MATHEMATICA
ok[1]=True; ok[n_]:=And@@(Mod[#, 3]==2&)/@FactorInteger[n][[All, 1]]; Select[Range[200], ok] (* Vincenzo Librandi, Aug 21 2012 *)
PROG
(Magma) [n: n in [1..300] | forall{d: d in PrimeDivisors(n) | d mod 3 eq 2}]; // Vincenzo Librandi, Aug 21 2012
CROSSREFS
Sequence in context: A102798 A247886 A244991 * A066208 A357981 A169743
KEYWORD
nonn
STATUS
approved